The US military has gone from using your SSN as ID to using a serial number (again). When DW gets her new ID card I'll have to get one also to reflect the new number. Hers will be my number with the ending -01.

other tips -

Never carry your SS card with you.
Think about using RF blocking sleeves to carry the cards you do carry.
Don't carry all 13 credit cards the average household has (we have 2, more than enough as they are both paid off monthly).
Never leave your purse in the shopping cart unattended. Carry it, preferably cross slung - right shoulder/left hip.
Go through your purse/wallet. If you haven't used it in 6 months, dump it. The item, not the purse/wallet.
Carry a card with your phone numbers in your purse/wallet. A good Samaritan can call you and arrange a return. And make that return at a police station - ya never know.